382 



ZOOLOGY 



SFX'T. 



solid. To each side of the rachis is attached a kind of membrane 

 forming the expanded part of the feather and composed of harhs — 

 delicate, thread-like structures which extend oblicjuely outwards 

 from the rachis. In an uninjured featlicr the barbs are closely 

 connected so as to form a continuous sheet, but a moderate amount 

 of force separates them from one another, and it can readily be 

 made out with the aid of a magnifying glass that they are bound 

 together by extremely delicate obli([uo filaments, the harlndcs, 

 havino- the same oreneral relation to the barbs as the barbs theni- 

 selves to the rachis. 



The precise mode of interlocking of the barbs can be made out 

 only by microscopic examination. Each barb (Fig 1024, A) is a 

 very thin and long plate springing by a narrow base from the 

 rachis, and pointed distally. From its upper edge — the edge 



I 



Flo. 1024. — Structure of Featber. A, small portion of feather witli pieces of two barlis, each 

 having to the left three distal harbulcs, and to the right a number of proximal liarbules, many 

 of them belonging to adjacent barbs. B, hooklet of distal barbule interlocking with tiangc of 

 proximal barbule. 0, two adjacent proximal barbules, D, a distal barbule. (From He<idley, 

 after Pycraft.) 



furthest from the body of the Bird — spring two sets of barbules, a 

 'proximcd set (C) directed towards the base of the feather, and a 

 distal set (D) towards i*"s tip. Owing to their oblique disposition 

 the distal barbules of a given barb cross the proximal barbules of 

 the next, each distal barbule being in contact with several proximal 

 barbules of the barb immediately distal to it (A). The lower edge 

 of the distal barbule is produced into minute hooJdets (D) : in 

 the entire feather the booklets of each distal barbule hook over 

 prominent Jlanges of the proximal barbules with which it is in 



